proper/best type for storing latitude and longitude

Question

In a system level programming language like C, C++ or D, what is the best type/encoding for storing latitude and longitude?

The options I see are:

• IEEE

Answer 1

Might the problems you mentioned with floating point values become an issue? If the answer is no, I'd suggest just using the radians value in double precision - you'll need it if you'll be doing trigonometric calculations anyway.

If there might be an issue with precision loss when using doubles or you won't be doing trigonometry, I'd suggest your solution of mapping to an integer range - this will give you the best resolution, can easily be converted to whatever display format you're locale will be using and - after choosing an appropriate 0-meridian - can be used to convert to floating point values of high precision.

PS: I've always wondered why there seems to be no one who uses geocentric spherical coordinates - they should be reasonably close to the geographical coordinates, and won't require all this fancy math on spheroids to do computations; for fun, I wanted to convert Gauss-Krüger-Koordinaten (which are in use by the German Katasteramt) to GPS coordinates - let me tell you, that was ugly: one uses the Bessel ellipsoid, the other WGS84, and the Gauss-Krüger mapping itself is pretty crazy on it's own...